Advertisements
Advertisements
Question
Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.
Advertisements
Solution
The focal length of a combined lens can be determined by the formula
`1/f =(mu -1)(1/R_1 - 1/R_2)`
Here, R_2 =∞ and f =0.3m
`1/0.3 =( mu-1) xx 1/R_1`
`R_1 = 0.3(mu-1)`
`=0.3(1.5 -1)`
` =0.3 xx 0.5`
`= 0.15m`
`=15 cm`
APPEARS IN
RELATED QUESTIONS
Define the power of a lens.
What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
A converging lens has focal length of 50 mm. What is the power of the lens?
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
Consider the situation described in the previous problem. Where should a point source be placed on the principal axis so that the two images form at the same place?
If focal length of a convex lens is 20 cm at what is the power of the lens?
A convex lens with radii of curvature R1 = R2 is immersed in water. Assuming that the refractive indices of glass and water are 3/2 and 4/3 respectively, its focal length f1 in comparison to that in air, f, is ______.
The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.
